textproduct: Albany

WHAT HAS CHANGED

Marginal Risk (level 1 of 5) introduced in the Day 2 SPC Convective Outlook focused in the western Adirondacks. Damaging winds is the primary hazard from any severe storms.

Lowered dew points Thursday and Friday to reduce coverage of potentially hitting heat advisory criteria, especially on Thursday. Changed shower/thunderstorm wording on Thursday to coverage (isolated/scattered) rather than probabilistic (slight chance/chance) given weak forcing. WPC also introduce a marginal risk for excessive rainfall in far northern Herkimer and Hamilton County on Thursday.

KEY MESSAGES

1) The combination of increasing heat and humidity presents a low chance for isolated areas where heat index values near 95 degrees in the Greater Capital District on Thursday. However, given isolated nature, heat advisories are unlikely.

2) There is a low to medium chance for showers and thunderstorms tomorrow and Friday as a cold front approaches with a marginal risk (level 1 of 5) for severe thunderstorms tomorrow in the western Adirondacks.

DISCUSSION

KEY MESSAGE 1...

After a dry and very pleasant day today, southwest flow redevelops tomorrow as high pressure pushes off the East Coast. 850 hPa isotherms rise to +16C to +18C as subtle warm front lifts northeastward from the mid-Atlantic. Deep enough mixing as morning sun mixes with increasing afternoon clouds should support temperatures warming into the mid-80s to around 90 in valley areas. Latest probabilistic guidance shows a 30 to 60% chance that valley areas from the Greater Capital District into the Lake George/Saratoga Region will reach or exceed 90 degrees on Thursday. This combined with increasing humidity values gives a medium chance for heat index values to reach the low to mid 90s. Given the isolated nature of the heat index values around 95 degrees plus HeatRisk categories mainly only around Minor (level 1 of 4), heat advisories are unlikely.

KEY MESSAGE 2...

A very warm and increasing humid air mass will be in place both Thursday and Friday as weak boundaries and height falls approach ahead of a broad trough slowly shifting eastward through the Great Lakes. Despite the warm/humid air mass, latest medium range guidance continues to show overall low instability values both days mainly near or under 1000 J/kg likely due to weak lapse rates and rather warm temperatures aloft from weak upper level forcing. Deep layer shear values, however, are still sufficient to support some organized convection ranging 25-30kts tomorrow and increasing to 30-35kts on Friday as a cold front approaches and the trough moves overhead. Given a pressure trough approaching from Western NY/southern Canada and a few shortwaves tracking mainly near and south of I-90 on Thursday, shower and thunderstorm coverage looks isolated to scattered. Convection looks to initiate during the typical peak heating hours. Highest chances for showers/storms remain south of I-90 closer to the incoming shortwaves and in the western Adirondacks as the leading edge of the trough/stronger winds aloft slide eastward. The latest HREF shows a 10% chance for updraft helicity values to exceed 20m/s Thurs P.M, suggesting some stronger updraft potential. Latest SPC Day 2 Convective Outlook introduced a marginal risk for severe weather into the North Country and Western NY, grazing our western Adirondacks areas. Damaging winds are the primary hazard from any severe storms.

Cloud coverage increases on Friday so temperatures should fall a few degrees but humidity remains elevated which will support instability values similar to Thursday. Overall forcing remains weak with broad troughing from the Great Lakes shifting overhead but with minimal height falls and a weak sfc cold front also approaching. The increased sfc forcing should lead to more widespread precipitation Friday afternoon into the evening from west to east. While deep layer shear increases, overall instability still looks low given warm temperatures aloft and weak lapse rates (especially if cloud coverage remains rather high) so severe weather potential again appears low. Latest SPC convective outlooks keep the Northeast just in a general thunder both days with WPC outlining far northern Herkimer/Hamilton County in a marginal risk for excessive rainfall Thurs into Thurs night likely due to incoming cold front. Even still, we do not expect flooding issues.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Through 12Z Thu...Patchy dense fog early this morning at ALB and GFL has ended at ALB with fog and low cigs at GFL dissipating by 13 UTC. Then, high pressure will support VFR conditions through at least 03 UTC. Skies start off clear tonight supporting additional radiational cooling potential; however, incoming mid and upper level clouds may mitigate fog formation. Given uncertainty, only show MVFR vis developing at GFL towards 05 UTC. Otherwise, winds remain light and variable through the end of the TAF period.

Outlook...

Thursday Night: Low Operational Impact. Slight Chance of SHRA...TSRA. Friday: High Operational Impact. Likely SHRA...TSRA. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Monday: Low Operational Impact. Slight Chance of SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.